有没有办法知道在VB.NET如果处理程序已注册的事件？ [英] Is there a way to know in VB.NET if a handler has been registered for an event?

问题描述

在C＃中，我可以测试这个...

In C# I can test for this...

public event EventHandler Trigger;
protected void OnTrigger(EventArgs e)
{
    if (Trigger != null)
        Trigger(this, e);
}

有没有办法做到这一点在VB.NET？测试空我的意思吗？

Is there a way to do this in VB.NET? Test for null I mean?

更多信息

我忘了提。我已经写在C＃类，但我写我的单元测试在VB.NET。

I forgot to mention. I have classes written in C# but I am writing my unit tests in VB.NET.

我想这在单元测试...

I am trying this in the unit test...

If myObject.Trigger IsNot Nothing Then  
    ''#do something
End If

这是造成编译时错误它说......公共事件触发一个事件，不能直接调用。使用RaiseEvent语句引发一个事件。

This is causing a compile time error which says ... "Public Event Trigger is an Event and cannot be called directly. Use the RaiseEvent statement to raise an event."

赛斯

推荐答案

有问题的 1129517 。

由于包含事件类是用C＃编写，委托语义仍然适用，而那些技术应该为你工作。但是，你需要转换的源VB.NET的单元测试。

Since the class that contains the Event was written in C#, the delegate semantics do apply, and those techniques should work for you. However, you'll need to translate the source to VB.NET for your unit test.

考虑下面的类在C＃程序集：

Given the following class in a C# assembly:

public class Triggerific
{
    public event EventHandler Trigger;

    private static void OnTriggerTriggered(object sender, EventArgs e)
    {
        Console.WriteLine("Triggered!");
    }

    public void AddTrigger()
    {
        Trigger += OnTriggerTriggered;
    }
}

下面是一些VB.NET code，将正确地确定是否处理程序注册了触发事件：

Here is some VB.NET code which will correctly determine if a handler was registered for the Trigger event:

<TestMethod()> _
Public Sub TriggerTest()
    Dim cut As New Triggerific
    cut.AddTrigger()

    Assert.IsNotNull(GetEventHandler(cut, "Trigger"))
End Sub

Private Shared Function GetEventHandler(ByVal classInstance As Object, ByVal eventName As String) As EventHandler
    Dim classType As Type = classInstance.[GetType]()
    Dim eventField As FieldInfo = classType.GetField(eventName, BindingFlags.GetField Or BindingFlags.NonPublic Or BindingFlags.Instance)

    Dim eventDelegate As EventHandler = DirectCast(eventField.GetValue(classInstance), EventHandler)

    ' eventDelegate will be null/Nothing if no listeners are attached to the event
    Return eventDelegate
End Function

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